6.0

CPU Compatibility and EVC
vCenter Server performs compatibility checks before it allows migration of running or suspended virtual
machines to ensure that the virtual machine is compatible with the target host.
vMotion transfers the running state of a virtual machine between underlying ESXi systems. Live migration
requires that the processors of the target host provide the same instructions to the virtual machine after
migration that the processors of the source host provided before migration. Clock speed, cache size, and
number of cores can differ between source and target processors. However, the processors must come from
the same vendor class (AMD or Intel) to be vMotion compatible.
NOTE Do not add virtual ESXi hosts to an EVC cluster. ESXi virtual machines are not supported in EVC
clusters.
Migrations of suspended virtual machines also require that the virtual machine be able to resume execution
on the target host using equivalent instructions.
When you initiate a migration with vMotion or a migration of a suspended virtual machine, the Migrate
Virtual Machine wizard checks the destination host for compatibility and produces an error message if
compatibility problems will prevent migration.
The CPU instruction set available to the operating system and to applications running in a virtual machine
is determined at the time that a virtual machine is powered on. This CPU feature set is based on the
following items:
n
Host CPU family and model
n
Settings in the BIOS that might disable CPU features
n
ESX/ESXi version running on the host
n
The virtual machine's compatibility setting
n
The virtual machine's guest operating system
To improve CPU compatibility between hosts of varying CPU feature sets, some host CPU features can be
hidden from the virtual machine by placing the host in an Enhanced vMotion Compatibility (EVC) cluster.
NOTE You can hide Host CPU features from a virtual machine by applying a custom CPU compatibility
mask to the virtual machine, but this is not recommended. VMware, in partnership with CPU and hardware
vendors, is working to maintain vMotion compatibility across the widest range of processors. For additional
information, search the VMware Knowledge Base for the vMotion and CPU Compatibility FAQ.
Create an EVC Cluster
Create an EVC cluster to help ensure vMotion compatibility between the hosts in the cluster.
When you create an EVC cluster, use one of the following methods:
n
Create an empty cluster, enable EVC, and move hosts into the cluster.
n
Enable EVC on an existing cluster.
VMware recommends creating an empty EVC cluster as the simplest way of creating an EVC cluster with
minimal disruption to your existing infrastructure.
Prerequisites
n
You must be connected to a vCenter Server system with the vSphere Client.
n
Before you create an EVC cluster, ensure that the hosts you intend to add to the cluster meet the
requirements listed in the vCenter Server and Host Management publication.
vSphere Administration with the vSphere Client
128 VMware, Inc.